One of the significant advantages of LED lighting technology is the ability to work with solid state circuits and control the light output in a very dynamic way. High mast lighting systems can incorporate multiple control strategies for automated or remote switching or dimming operation. Lighting controls, including occupancy controls, photocontrols, time clocks, and energy management systems, are often installed at the circuit or luminaire level. LED drivers are configured to interpret control signals to dim or switch the LEDs. The control signals can be communicated to the luminaires using a variety of wired and wireless protocols, such as 0-10V, DALI, and ZigBee. Both local and centralized control systems can be integrated into high mast lighting systems. Luminaires or fixtures can be assigned to different zones, or areas of controls to maximize the flexibility of lighting control. Networked control systems combine software and hardware to provide a wide range of options for more adaptive lighting control and sophisticated user interactivity.
Light Source
Recently, high mast luminaires that incorporate mid-power LEDs have been creeping into the market. What make mid-power LEDs appeal to lighting manufacturers are their low price points and high luminous efficacies. The problem is, mid-power LEDs are plastic leaded chip carrier (PLCC) packages that are prone to package material deterioration and rapid performance degradation in high power operating environments. The high efficacy of mid-power LEDs is founded on the high reflectivity of the plastic cavity and plated lead frame. At high temperatures and intense light levels, irreversible thermal oxidation and photodegradation in plastics, in particular polyphthalamide (PPA) and polycyclohexylenedimethylene terephthalate (PCT), can occur. The epoxy molding compound (EMC) has an improved thermal stability, but only to a limited extent. Silver plated lead frame which is exposed to the micro climate containing sulfur compounds will corrode. All these lead to a significant drop in light extraction efficiency. Not only do mid-power LEDs have a poor lumen maintenance and color stability, their reliability is a serious concern in outdoor environments. Leadframe corrosion can lead to an open contact because a mechanical separation between the bond wire and the connecting lead. The bonding wire that connects the lead frame to the LED electrodes can break due to internal stress, environmental vibration, thermal cycling, and electromigration.
For dependable lighting with high mast lights, high power LEDs deserve their prices. The ceramic-based LED packages are unencumbered with thermally unstable packaging materials. Unlike plastic-based mid-power LED, high power LEDs have high drive current capability and can survive a significantly higher operating temperature without compromising luminous efficiency and lifespan. The high power family also includes chip-on-board (COB) packages which are multi-die LED array typically used in applications needing a high lumen package from a light emitting surface with high emission uniformity. In addition to their high thermal performance, both high power ceramic LEDs and COB LEDs provide highly reliable interconnectivity between the package and MCPCB. The reliability of the interconnects between the LED package and printed circuit board is very critical in ensuring the overall reliability of an LED luminaire.
